The invention relates to modulating hair growth in mammals.
A main function of mammalian hair is to provide environmental protection. However, that function has largely been lost in humans, in whom hair is kept or removed from various parts of the body essentially for cosmetic reasons. For example, it is generally preferred to have hair on the scalp but not on the face.
Various procedures have been employed to remove unwanted hair, including shaving, electrolysis, depilatory creams or lotions, waxing, plucking, and therapeutic antiandrogens. These conventional procedures generally have drawbacks associated with them. Shaving, for instance, can cause nicks and cuts, and can leave a perception of an increase in the rate of hair regrowth. Shaving also can leave an undesirable stubble. Electrolysis, on the other hand, can keep a treated area free of hair for prolonged periods of time, but can be expensive, painful, and sometimes leaves scarring. Depilatory creams, though very effective, typically are not recommended for frequent use due to their high irritancy potential. Waxing and plucking can cause pain, discomfort, and poor removal of short hair. Finally, antiandrogens--which have been used to treat female hirsutism--can have unwanted side effects.
It has previously been disclosed that the rate and character of hair growth can be altered by applying to the skin inhibitors of certain enzymes. These inhibitors include inhibitors of 5-alpha reductase, ornithine decarboxylase, S-adenosylmethionine decarboxylase, gamma-glutamyl transpeptidase, and transglutaminase. See, for example, Breuer et al., U.S. Pat. No. 4,885,289; Shander, U.S. Pat. No. 4,720,489; Ahluwalia, U.S. Pat. No. 5,095,007; Ahluwalia et al., U.S. Pat. No. 5,096,911; Shander et al., U.S. Pat. No. 5,132,293; and Shander et al., U.S. Pat. No. 5,143,925.
The growth of hair results from many complex and interactive processes. In one process sex steroid androgens, particularly testosterone, act on, for example, beard hair follicles on the face to stimulate hair growth. But these same androgens can inhibit hair growth on the scalp, particularly in those that have a genetic predisposition for male-pattern baldness or androgenetic alopecia.
Cytochrome P450s, epoxide hydrolases, glutathione-S-transferases, uridine diphosphate-glucuronosyltransferases (UGTs), and sulfotransferases (STs) are families of enzymes that are involved in the metabolism of xenobiotics and other substances that are endogeneous to the human body. Generally, the enzymes catalyze the conversion of a substrate (e.g., a particular steroid) to a form that is more readily eliminated from the body. For example, glutathione-S-tranferases catalyze the conjugation of the substrate with glutathione; UGTs catalyze the conjugation of substrate with glucuronic acid; and STs catalyze the conjugation of the substrate with a sulfonate moiety. It is believed that these substrate conjugates are more water soluble than the substrate itself, and thus more readily eliminated from the body. Some of these enzymes can be induced by compounds, such as 3-methylcholanthrene and phenobarbital.
Steroids are substrates for several isoforms of UGT, with overlapping specificities. For example, rat liver UGTr-3 catalyzes the glucuronidation of dihydrotestosterone, testosterone and .beta.-estradiol, whereas in addition to these steroids UGTr-2 also catalyzes 4-hydroxybiphenyl, chloramphenicol and 4-methylumbelliferone glucuronoconjugation (Chen et al., Biochem. 32: 10648-10657).